Well, that seems like a wasteful amount of time to spend on prototype products or functionality. It's up to you if you want to do that, but other people will likely out-manoeuvre you by being agile enough to iterate quickly.
No one is saying you have to needlessly screw things up. If you're writing things in an equally laborious but worse way, that's just being a bad programmer – nothing to do with tech debt.
Tech debt is more, say, "let's build this new bookmarking functionality by saving bookmarks locally" and then, later on, "let's make it more extensible by syncing them with the server, so we can build on it by e.g. using this information in our new recommendation algorithm".
It's about implementing things in a less complex but less extensible way, and perhaps a less feature-rich way, so as to more quickly validate user demand and thus iterate more quickly.
And yes, it's trivially true that you'll be slower than you could be otherwise by not doing this. You might think you're still faster than other people will be. I wouldn't bet my own money on that, but it's your prerogative to bet yours.
But I will not build a sync feature and not having alerting if it fails.
I will not write nee Features and will not think about a proper index.
If you do it right and actually learn those things from an early point those things become obvious.
And yes there is also that believe that a bug in production costs 10x what it would cost to find while developing.
Yes I'm aware of the fallacy that a manager might praise you if you are fast and accepts bug as a common normal thing.